Project Summary Insulin replacement therapy has saved numerous lives of Type 1 diabetic patients since it was established in the 1920's. Currently, multiple fast-, intermediate- and longer-acting insulins are available to patients. However, many patients on insulin replacement therapy do not achieve adequate blood glucose control as indicated by not reaching target HbA1c levels (<7%). Inter- and intra-patient variability is a major factor limiting the effectiveness of basal insulin therapy; this variability enhances the likelihood of hypoglycemia and reduces the dose of insulin that may be safely prescribed. An insulin therapy that is more convenient and less likely to induce hypoglycemia would lead to greater patient compliance. Thus, methods to deliver a flatter, more even dose of insulin, with smaller variability, and in a convenient format to increase compliance, has the potential to significantly improve glycemic control in diabetes patients. Extend Biosciences is harnessing the body's own natural systems to extend the half-life and increase the bioavailability of peptides following subcutaneous injection. In this Phase I SBIR grant, we propose to develop an ultralong-acting version of insulin using our technology and formulate it as a slow-release depot to achieve a once-weekly basal insulin replacement. Preliminary results show that our technology confers a longer half-life and increased bioavailability without affecting the function of insulin at the insulin receptor. We propose to establish the feasibility of a once-weekly basal insulin for the treatment of diabetes by achieving the following three specific aims. First, we will prepare three depot delivery methods with our long-acting insulin. Then, we will test these formulations in a rat model of type 1 diabetes. We will also examine the pharmacokinetics of these formulations in minipigs, an animal model that is more predictive of behavior in humans. Once fully developed, this insulin derivative would greatly benefit patients with diabetes by helping them manage their disease using a long-lasting, patient-friendly drug. More even dosing would lower the risks of hypoglycemia while improving control of blood glucose, thus reducing long-term diabetic complications such as cardiovascular disease, retinopathy, neuropathy, gastroparesis, and nephropathy.